1. Field of the Invention
The present invention relates to an insulator device interposed when coupling a car body with the upper portion of a piston rod of a shock absorber disposed in a strut type suspension system of an automobile and more particularly, to an improved insulator device including an asymmetrical relationship provided between the shape of the inner portion and the outer portion of rubber of the insulator device for controlling the variation state of the camber and tread so as to improve turning performance.
2. Description of the Prior Art
Generally, when the turning function of an automobile is to be upgraded so as to obtain running stability and pleasant ride feeling, most factors include not only a steering device but also collective cooperations among a suspension system including front wheels and other components. In such strut type suspension system, the insulator used in coupling the car body with the upper portion of a piston rod of a shock absorber not only plays for preventing the vibrations of a strut assembly from being transferred to the car body but also gives a great influence to the turning function of the automobile.
As shown in FIG. 1, such insulator includes a rubber C formed between the insulator housing A and a bearing case B, wherein inner and outer portions thereof have symmetrical shapes each other. Therefore, when impacts are imposed from car wheels, the rubber C is uniformly compressed in order to perform an action as shown by an imaginary arrow as shown in FIG. 1.
Thus if the automobile is subjected to bumping as shown by dotted lines of FIGS. 6(A) and 6(B), a camber is shifted to a negative state (-) to be return to a positive state (+) again and at the same time, a tread is slightly extended to be contracted again. Therefore, there are a number of problems such as, for example, the camber has a positive bias when performing a turning and gripping forces of the tires are reduced.
In order to overcome such disadvantages, Mazda Corporation, Japan has proposed an adding of a camber control link (not shown) to the suspension system. However, this method has a limitation because an installing space is limited, a weight increase is caused after the addition of the camber control link, and an operational improvement thereof is obtained through deformations of the link of a weaker mount having a weaker stiffness. Therefore, the operational certainty cannot be assured, the links require a great precision, and an aggravation of the riding stability and comfort can be invited. That is, a moving track of wheels relative to the car body can be satisfied to a certain degree through a proper designing. However, it has an intrinsic limitation in controlling variations of the camber and the tread when an automobile is subjected to bumping.